The new planet, called 51 Eridani b, is the first exoplanet discovered by the Gemini Planet Imager, a new instrument operated by an international collaboration headed by Bruce Macintosh, professor of physics at Stanford University.

To detect planets, NASA's Kepler sees their shadow. The Gemini Planet Imager instead sees their glow, which we refer to as direct imaging," said Macintosh, member of the Kavli Institute for Particle Astrophysics and Cosmology.

51 Eridani b is one of the best stars for imaging young planets. "It is one of the very youngest stars this close to the Sun. 51 Eri was born 20 million years ago, 40 million years after the dinosaurs died out," added study co-author Eric Nielsen, post-doctoral researcher at Stanford and the SETI Institute.

As far as the cosmic clock is concerned, 20 million years is young, and that is exactly what made the direct detection of the planet possible.

Once the astronomers zeroed in on the star, they blocked its light and spotted light reflecting off 51 Eridani b, orbiting a little farther away from its parent star than Saturn does from the Sun. The light from the planet is very faint - more than 3 million times fainter than its star - but Gemini can see it clearly.

Observations revealed that it is roughly twice the mass of Jupiter, half or less the mass of the young planets discovered to date.

All of these characteristics, the researchers say, point to a planet that is very much what models suggest Jupiter was like in its infancy. "Many of the exoplanets astronomers have imaged before have atmospheres that look like very cool stars. This one looks like a planet," Macintosh contended.

This planet really could have formed the same way Jupiter did - the whole solar system could be a lot like ours, he emphasised. The results were published in the prestigious journal Science.